The present invention relates in general to endoscopic surgery, and in particular, to trocars having shields or protectors for use in endoscopic surgical procedures.
The use of endoscopic procedures in surgery has become widely accepted. The term endoscopic as used herein is defined to include all types of minimally invasive surgical procedures including laparoscopic and arthroscopic procedures. Accordingly, numerous endoscopic instruments have been developed which allow the surgeon to perform complex surgical procedures with minimal incisions into the skin and tissue surrounding a particular body cavity or anatomical region. In order to introduce the endoscopic instrumentation into the body cavity, it is often necessary to puncture and cannulate the body cavity by using a trocar. Trocars are widely known in the art and typically consist of an obturator and a trocar cannula.
It is common for a sealing arrangement or sealing device to be used in association with the cannula to prevent the escape of fluid or gas during endoscopic procedures. During an endoscopic surgical procedure, the internal gas pressure must be maintained in order to successfully complete the procedure. In order to maintain the internal gas pressure while instruments are passed into and out of the trocars positioned in the abdominal cavity, sealing devices are required for both the instruments and for the trocar assemblies. It is desirable for such sealing devices to seal any opening within the trocar assembly when the obturator is withdrawn after puncturing the abdominal wall. It is also desirable to seal when other surgical instruments are inserted through the trocar cannula throughout the remainder of the surgical procedure. Furthermore, it is desirable that the sealing device maintain gas pressure in the abdominal cavity, despite numerous insertions and withdrawals of surgical instruments through the trocar cannula.
Current sealing devices for endoscopic instruments are typified by particular valve designs such as that described in U.S. Pat. No. 5,224,952 (Deniega et al.). This design includes a spring loaded valve in combination with a sealing gasket to conform to the cross section of the surgical instrument inserted through the trocar. This two part valve assembly performs adequately as a seal but may be more complex than truly desired. U.S. Pat. No. 5,141,498 (Christian) shows at least three flexible leaflets, and U.S. Pat. No. 4,424,833 (Spector et al.) shows a sponge type valve with three connecting slits. Multiple leaflet and multiple slit valves may seal well when a surgical instrument is not inserted through them but will tend to create gaps around inserted instruments having circular cross sections and will also tend to cause inversion of their sealing surfaces when the instruments are withdrawn. Inversion of the sealing surfaces is likely to cause gaps between the sealing surfaces resulting in gas leakage through the seal. U.S. Pat. No. 5,242,412 (Blake) shows a duck bill valve design applied to a trocar device. This design provides a straight single slit to seal against a surgical instrument. U.S. Pat. Nos. 4,475,548 (Muto); 4,809,679 (Shimonaka et al.); and 4,143,853 (Abramson) show single slit designs also. A single slit valve is also subject to a lack of conforming to circular cross-section shapes and to inversion upon withdrawal of surgical instruments.
Variations of the single slit design are shown in U.S. Pat. Nos. 4,798,594 (Hillstead); 4,177,814 (Knepshield et al.); and 4,673,393 (Suzuki et al.). The variations shown in these patents encompass three slits radiating from the seal center and possess similar characteristics as the single slit regarding sealing around circular instruments and eversion. Other surgical valves include specialized designs typified by heart valves shown in U.S. Pat. Nos. 4,364,127 (Pierce et al.); 3,861,416 (Wichterle); and 4,222,126 (Boretos et al.). These valves are designed to allow one direction flow of heavy liquids and include at least three flaps. Such valves are not intended to seal around surgical instruments against loss of gas pressure.
A study of these references indicates a need for a simpler one piece assembly for use in trocars to seal against gas pressure during endoscopic surgical procedures. In addition, it is desirable to have a one piece assembly with a simple design which would not require an excessive force to insert an instrument through it and would resist inversion of the sealing edges once the surgical instrument is withdrawn.
One known seal assembly design which has been developed in an attempt to solve the sealing needs outlined above is disclosed in U.S. Pat. No. 5,330,437 (Durman) which is incorporated herein by reference. This seal assembly design includes a one piece assembly having a duck bill valve in a S-shaped configuration. Although this particular seal design has proved to be successful in addressing some of the drawbacks found in the other known sealing devices, as will be shown later in this disclosure, this seal design can be improved in order to significantly reduce forces to insert and extract surgical instruments.
Additionally, trocars may have a protective element around the obturator which covers the sharp piercing tip of the obturator prior to and after insertion, and also after removal of the obturator and trocar cannula. The protective element is often referred to as a safety shield or protector.
One type of trocar utilizes a safety shield and is typically inserted by pressing the distal end of the trocar assembly against the outer skin of the patient with sufficient force to cause the piercing end of the obturator to pierce through the skin, underlying fat, muscle and fascia into the body cavity. The trocar is permitted to penetrate into the body cavity because the safety shield is retracted proximally thereby exposing the sharp piercing tip. However, upon completing the penetration, the safety shield automatically returns to its protective position covering the piercing tip. This type of trocar is a fully returnable safety shielded trocar. Once the surgeon has properly positioned the trocar within the body cavity, the obturator together with the safety shield are removed and the trocar cannula is then available as a pathway, e.g., for insertion of endoscopic instrumentation. U.S. Pat. No. 5,387,197 (Smith et al.) describes this type of trocar.
With current fully returnable safety shielded trocars, it may be necessary to remove the cannula handle from the obturator handle to "reload" the shield on the trocar obturator for those instances where the trocar has not completely penetrated into the body cavity. In this fashion, therefore, it is necessary to perform an extra step while the obturator tip is inserted within pneuoperitoneum.
Yet, in some procedures it may be desirable to utilize trocars without a safety shield or to utilize a trocar design wherein the trocar obturator is nonshielded at the time when the trocar obturator is placed within the trocar cannula. Thus, upon coupling of the shielded obturator and the cannula, the shield will be retracted thereby exposing the piercing tip of the obturator. This type of trocar can be referred to as an assembly actuated trocar.
An assembly actuated trocar prevents the shield from returning to its protective position upon placement of the obturator within the cannula. U.S. Pat. No. 5,248,298 (Bedi et al.) describes this type of trocar. In this way, the user is able to slightly withdraw the trocar from the pierced tissue, and then continue penetrating through remaining tissue layers. This prevents what is commonly referred to as "tenting" of pneumoperitoneum. In this fashion, tenting can be reduced while still adequately providing access to the body cavity.
In an effort to eliminate problems with tenting or to reduce cost from surgery, surgeons often utilize trocars that do not employ a safety shield since these types of trocars are generally less expensive than fully returnable safety shielded trocars. However, for those procedures that utilize trocars without a safety shield, there is a possibility that the obturator tip could cut a person handling the trocar or damage the trocar seal assembly or other components of the instrument.
Presently, there is no known trocar that provides a low cost option to the surgeon while maintaining the ability to protect the obturator piercing tip with a shield or protector up until the time when the obturator is coupled to the proximal end of the cannula.
Moreover, there is no known trocar that utilizes a seal assembly that significantly reduces the amount of force required to insert and extract surgical instruments.